body {
  background-color: #f5f5f5;
}

.wrapper_01 {
  width: 1100px;
}

.wrapper_02 {
  width: 980px;
  margin: 0 auto;
}

.back-top {
  position: sticky;
  bottom: 160px;
  left: 83%;

  width: 49px;
  height: 44px;
  background-position: -265px -47px;
  background-image: url(https://s2.music.126.net/style/web2/img/sprite.png?e0e6f266231052e44b78be5ca13abf77);
}